Measuring the angle of arrival of incoming signals in the past has been accomplished through the utilization of Adcock antennas and the like which involve antennas that extend above the top of vehicles that increases the visibility of the vehicle, aircraft, or vessel.
There is therefore need to provide a conformal antenna from which angle of arrival of incoming signals can be determined, and to do so regardless of the polarization of the incoming signal. It is noted that it is possible to obtain the angle of arrival of an incoming signal with a high degree of accuracy, but this accuracy is degraded significantly if one does not know the polarization of the incoming signal. This is especially true when deriving angle of arrival from left hand circular polarized and right hand circular polarized components of the received signal. Thus, it is important to be able to ascertain the angle of arrival of an incoming signal independent of the polarization of the incoming wave.
While co-pending patent applications Orientation-Independent Antenna with Shorts (2006-0003), Ultra Compact UHF Satcom Antenna (2006-0005), and Orientation-Independent Antenna (2007-0058) assigned to the assignee hereof and incorporated herein by reference relate to orientation-independent antennas utilizing miniature volumetric quadrametric geometry, it is not entirely clear how these antennas can be configured for a direction finding function and be polarization independent. Moreover, how to preserve these direction finding functions when providing a miniature antenna conformal to a surface in which it is embedded presents some challenges.
Thus, while a Satcom version of the orientation-independent miniature antenna is described in the above identified co-pending patent applications, when attempts are made to embed these antennas in a cavity to make the antenna into a conformal antenna, how one obtains polarization independence to permit accurate angle of arrival measurements is unclear. This is because the complicated phasing used to make these antennas orientation-independent is not applicable to a conformal antenna used for polarization-independent direction finding.